## 32.6. Regular Expressions: Matching a Character with a Character Set

The simplest character set is a single character. The regular expression `the` contains three character sets: `t`, `h`, and `e`. It will match any line that contains the string `the`, including the word `other`. To prevent this, put spaces (``) before and after the pattern: `the`.

You can combine the string with an anchor. The pattern `^From`:`` will match the lines of a mail message (Section 1.21) that identify the sender. Use this pattern with grep to print every address in your incoming mailbox. [If your system doesn't define the environment variable `MAIL`, try /var/spool/mail/$USER or possibly /usr/spool/mail/$USER. -- SJC]

`$USER` Section 35.5

>     % grep '^From: ' $MAIL

Some characters have a special meaning in regular expressions. If you want to search for such a character as itself, escape it with a backslash (`\`).

-- BB

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